ANTLR to run on Cygwin and GCJ

I've been trying to get ANTLR 2.7.4 to run under Cygwin with GCJ. After trying to piece information together, I've finally found a recipe that makes it work.

For those who don't know ANTLR: it's a replacement for the lex/yacc combination. Unlike YACC, which is a bottom up parser, ANTLR uses a TOP-DOWN parsing approach. There is a lot of information available on the ANTLR website. If you're interested in parser generation, you certainly should have a look. My goal is to write an ANTLR compatible grammar for VHDL.

Back to the topic: ANTLR comes with a standard ./configure script. It executes fine, until, during compilation, there is an error related to AWT in directory base/antlr/debug/misc. AWT seems to be a JAVA standard library.

Some googling, resulted a link that shows how to work around the error.

I tried this, but probably because some things in my path weren't set correctly (I think), this didn't work very well either. I was able to create a libantlr.so file (see step 4 of that page), but step 5 broke down. Step 5 relies on a file called antlr/Tool.class, which doesn't exist in the ./antlr directory but in the antlr.jar file instead (a jar file is a tar-like library in which .class files can be gathered, I think.)
In the end, I got it to work by un-jarring all the files and simply bypassing the creation of a shared library.

Here's what I did: (basedir is the directory where you can find ./configure)

1. Install gcj (through the setup.exe on cygwin.com)
   
2. Download the tar files of the latest version of ANTLR (2.7.4 in my case) and untar it in a local directory.
   
3. Run ./configure --prefix=install dir. While we do not need to configure to compile the antlr executable, we do need it to compile the support C++ libraries. Do NOT run make after configure!
   
4. Delete AWT dependent code:
   cd basedir/antlr/debug
rm -fr misc
   
5. cd basedir
   
6. Un-jar all the files in the antlr.jar, back into their original position.
   jar xfv antlr.jar
   
7. Compile everything into an executable
   gcj --main=antlr.Tool `find antlr -name "*.class"` -o cantlr
   If all is well, you will see a bunch of warnings on your screen that, I assume, you can safely ignore. The end result is a file called cantlr.exe).
   
8. Test the executable by running it (./cantlr). You should see a bunch of lines with program information.
   
9. Move this file to a place somewhere in your path (e.g. /usr/local/bin)
   

At this point, we have created that main executable that will convert a .g grammar file into a set of Java, C# or C++ files. These newly generated files, however, rely on base classes that are also part of the ANTLR distribution. For C++, we need to build a library that contains the compiled based classes.

1. cd basedir/lib/cpp
   
2. Build the C++ library. This step won't work if you previously didn't run ./configure.
   make
   
3. If everything went fine, then the ./src directory will contain a file called libantlr.a. Now install the library and include files to the place that was originally indicated during the ./configure step.
   make install
   

The next step is to test if now have a fully working system.

1. cd basedir/examples/cpp/calc
   
2. The standard Makefile will not know where to find the antlr executable. As a work around, just generate all files by manually invoking antlr.
   cantlr calc.g
   A set of C++ files will now be generated.
   
3. make
   
4. If everything went fine, you will now see a fresh set of executables!
   

This is how I got the system work for me while using GCJ and Cygwin. I'm pretty sure that the same procedure will also work in a Solaris or Linux environment...